1. Field of the Invention
This invention relates to the field of measuring devices. More particularly, this invention relates to the field of measuring devices such as measuring rulers especially adapted to measuring small distances for instance, distances on the order of one-hundredth of an inch.
2. Background of the Invention
The need to accurately measure distances between various points has been with man's civilization from the very beginning. Society as a whole and particularly art and science is based in large part upon the knowledge of distance. For accuracy, elongated strips of materials having a straight measuring edge have been used to measure these distances where indicia of measured units are imparted along the straight edge to permit the strip, called a measuring ruler or tape, to be held spanning between the measured points and direct visual reading taken place of the distance therebetween. The strips may be flexible or inflexible; some of the flexible strips may be windable on a reel. Some of the materials usable for the strips are wood, plastic, steel and plastic-coated cloth. The indicia may be imparted by printing, chemical etching, stamping, silkscreening and photoengraving.
In whatever culture one looks, one can percieve a unit of measure, such as the yard for English-speaking countries and the meter for others. Both of these units have been subdivided into very small units, inches and its subcomponents (hundredths and thousandths of an inch) and centimeters and its subcomponents (millimeters and decimal parts thereof). In each of these cases, the measuring ruler is used more often than any other device.
In the general makeup of measuring rulers, a unit, for instance an inch, is subdivided into a number of subunits representing a division of the unit, for instance one-half, one-quarter, one-eighth, one-sixteenth and so on. The space between the one-inch units represented by these particular subunits are visually observed by locating the distance to be measured on the straight edge, having one distance measuring point set at zero on the scale and thereafter counting the number of subdivisions between the zero reference on the scale and the other point and reading directly therefrom the distance in units and subunits. In general, the distance between the unit of measure on the scale is subdivided by straight narrow lines, normal or perpendicular to the straight measuring edge, and one visually observes and mentally counts the number of subdivisions between the points to be measured.
When measuring distances between measured indicia on a small sclae, it is difficult to visually and mentally coordinate the number of spaces between the points to be measured because of the plurality of dividing lines that interrupt the spaces that make up the subunits. Further, closely spaced measuring indicia are just hard to count because of their plurality and closeness. Even where the length of the indicia lines have been altered to show groupings of subdivisions, such as for 1/16th lines being grouped by end lines showing a quarter-inch, it is difficult to count the closely spaced dividing lines. Finally, the conventional division of an inch on a measuring rule is difficult to read down to one-hundredths of an inch because of the width and interruption of the lines separating the distances therebetween.
The prior art has made many attempts to facilitate measurements on scales where these sort of problems have arisen, see U.S. Pat. Nos. 289,512; 861,799; 1,687,429; 3,202,129; 4,247,986 and United Kingdom Pat. No. 12,395. While these prior art attempts have produced some readability in some scale measurements, none have been able to completely satisfy all of the aforesaid problems.